US1854432A - Generation of electric waves - Google Patents

Description

April 1932- G. M, THURSTON 1,854,432

' GENERATI0N OF ELECTRIC WAVES Filed-Aug. 1s 1927 z Sheets-Sheet 1 Ha a3 Arron/var April 19, 1932. I G. M. THURSTON 1,854,432

GENERATION OF ELECTRIC WAVES Filed Aug. 18. 1927 ,2 Sheets-Sheet 2 f JWM Arron/var Patented Apr. 19, 1932 ITED STATES PATENT OFFICE GEORGE E. THURSTON, OF NEW YORK, Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A'CORPOBATION OF NEW YORK GENERATION OF ELECTRIC WAVES Application filed August 18, 1927. Serial No. 213.778.

This invention relates to generation of electric waves.

cillator, operating at a given frequency, produces a harmonic wave of the given frequency and impresses the harmonic wave on a second oscillator tuned approximately to the harmonic frequency. The harmonic power from the first oscillator pulls the second oscillator into step, even though the pulling power may be very much smaller than the.

power in the second oscillator. Thus, a crystal controlled oscillator of relatively low frequency and power can stabilize the frequency of an oscillator of relatively high frequency and power.

If desired, the second oscillator can produce a harmonic of its base frequency, and impress the harmonic on a third oscillator adjusted to oscillate approximately at the frequency of the latter harmonic. The power from the second oscillator can pull the third into step, even though pf lessmagnitude than the power in the third oscillator. Similarly, four or more oscillators may be employed, each after the first being controlled by a harmonic from the preceding oscillator.

Systemsof this type have important advantages over a system comprising an oscillator feeding non-oscillatory harmonic pro-.

ducers or transmitters. For example, they require less power, and also they utilize singing and hence avoid any necessity for preventing singing in high frequency amplifier circuits even though the frequency of the second or subsequent oscillators may be higher than the maximum frequency at which crystals can be operated satisfactorily.

Instead of having the controlling harmonics produced in the oscillators themselves, non-oscillatory harmonic producers (that is, harmonic generators which do not produce self-sustained oscillations) may be inserted between the oscillators, to control the second oscillator from the first, etc.

Other objects and aspects of the invention will be apparent from the following description and claims.

In the drawings, Fig. 1 is a circuit diagram of a system embodying one form of the invention; Fig. 1A indicates a modification which may be made in the system of Fi 1; Fig. 2 is a circuit dia ram of another orm of the invention; and gram of still another form of the invention.

In Fig. 1 an oscillator O1 comprises an iig. 3 is a similar dia-' electric space discharge tube 1. The fundamental frequency of the oscillator is determined largely by the capacity C and the inductance L connected in parallel in theplate circuit of the tube. The inductaifte coil L is coupled to a feedback coil 10 in the grid circuit of the tube.

A harmonic of the oscillator frequenc is selected by'the capacity C and the in notance L in parallel in the plate circuit, and is impressed on the grid circuit of an .electric space discharge tube oscillator O2.

The oscillator O2 comprises an electric discharge tube 2 having a capacity C8 and an inductance L in parallel in its plate circuit. The inductance coil L is coupled to the feedback coil 15 in the grid circuit of the tube 2. Oscillator O-2 tends to oscillate at a frequency set by L and C 'at approximately the desired harmonic of the first oscillator and as near to the harmonic selected by L and C as convenience in the setting permits. The harmonic power from the first oscillator pulls the second one into step.

A harmonic of the frequency of the second oscillator is selected by the capacity C, and the inductance L in parallel in the plate circuit, and is impressed on the grid circuit of an electric space discharge tube power oscillator O3.

The oscillator O3 is shown as comprising two space discharge tubes 3 in parallel, coupled to an antenna 20 through an inductance coil 21 in the antenna and an inductance coil 22 in parallel with a capacity 23 in the plate circuit of the tubes. The coil 21 is coupled to a feedback coil 24 in the grid circuit of the tubes. The frequency of the power osc llator is determined largely by the antenna circuit and is very close to the resonant fre uency of L and C The harmonic power 0 the second oscillator pulls the third one into step with the harmonic frequency.

Plate current is supplied to the oscillators from source 25, that for tube 1 asslng through inductances L and L,,, that or tube assing through L and L and that for 3 passing through coil 22.

The grid circuit of each oscillator includes a condenser C, and a grid leak resistance R for supplying grid biasing potential. A condenser in each oscillator by-passes high frequency current around the plate current source and prevents that source from polarizin the oscillator grid or grids.

The frequency of the primary oscillator O-'1 may be stabilized in any satisfactory manner.

Undesired variations of the frequency of oscillator O-3 are prevented since the controlling harmonic frequencies from oscillators 0-1 and 0-2 synchronize oscillators O2 and O3 with those frequencies respectively.

Fig. 1A shows a modification of the connections shown in Fig. 1 between oscillators O1.and-O2. In Fig. 1A the capacity C, is across the secondary, instead of the primary, winding of the coupling transformer including inductance L In Fig. 2, a Colpitts oscillator O1' has its oscillation circuit, comprising inductance L in parallel with two series connected capacities 0' tuned approximately to the mechanical resonance frequency of a. piezo-electric crystal 40 which stabilizes the oscillator frequency. The source 25 supplies space current for tube 1 through a choke coil 41 that has high impedance for the frequencies gen erated by O-1. A condenser 42 prevents this source from polarizing the crystal.

A' harmonic of the oscillator frequency is selected by the capacity C and the inductance L in parallel in the plate circuit, and is impressed on the grid circuit of a Hartley os- Icillator O2'.

Oscillator O2 tends to oscillate at a frequency set by its oscillation circuit L and G at approximately the resonance frequency of L and G The harmonic power of the first oscillator pulls the second one into step.

A harmonic of the frequency of the second oscillator is selected by the capacity C, and the two inductances L';, and is impressed on the grid circuits of each of tubes 3 of a pushpull electric space discharge oscillator 0-3. The circuit constituted by capacity C in parallel with the two inductances L in series, is connected in series in the plate circuit of oscillator O-2. One of the coils L impresses the harmonic voltage fromoscillator 0-2 on the grid of one of tubes 3, and the other of the coils L 4 impresses the harmonic voltage on the grid of the other tube 3 in opposite phase or si The oscillator 5 3' tends to oscillate at a frequency set by its oscillation circuit L and G at approximately the resonance frequency of C, with inductances L The harmonic power of the second oscillator pulls the third one into step. The source 25 supplies space current to the tube 2 through one half of coil L and coils L;

The connection 45 to the inductance L is intended to represent any suitable load circuit for the oscillator O3', as for instance an antenna, or amplifier stages or a transmission line connected to an antenna.

' The inductance L is a bifilar coil comprising two strands 47 and 48. Condensers 49 connect the strands together at each end of the coil, and condenser 30 connects the strands together at the middle of the coil. Each of these three condensers has low impedance for frequencies of the order of the osc llation frequency; and the two strands 47 and 48 act as a single inductance at such fre uencies.

T e filaments of the two tubes 3 are conductively connected to the middle of strand 48. The grid of one of the two tubes is conductively connected to the filaments through a grid leak resistance and a portion of strand 48 at one side of the middle of the strand. The grid of the other tube 3 is conductively connected to the filaments through a grid leak resistance and a portion of strand 48 at the other side of the middle of the strand.

Source 25 supplies space current for the tubes 3, the current for one tube passing through one half of strand 47 and the current for the other tube passing through the other half of strand 47.

Undesired variations in the frequency of oscillator 0-3 are prevented since the controlling harmonic frequencies from oscillators O1 and 0-2 synchronize oscillators 0-2 and O-3' with those frequencies respectively.

The circuits described above may well serve as high power short wave generators and yet be free from high frequency amplifiers. The harmonics are produced in the oscillators themselves and taken out through appropriate circuits and impressed upon the succeeding oscillators. The primary oscillator may be stabilized in any satisfactory manner or crystal controlled as indicated in Fig. 2. In the systems of Figs. 1, 1A and 2, the primary osc llator does not have to be any of the arrangements shown, even though crystal controlled, but may be of any form in which there is an inductance in the circuit from which to get harmonics or in which an inductance or tuned circuit may be inserted to select the harmonics.

In Fig. 3 a tuning fork oscillator O-51, operating ata frequency of, for example,

1000 cycles a second, feeds an ampl'fier A62 which in turn feeds a harmonic generator HG-63. Oscillator 0-51 comprises a tuning fork 51 actuated by a magnet 52 which has its winding included in circuit with a coil 53, a suitable source of current 54 and an interrupting or resistance changing 'devce 55 mechanically actuated by a tine of the fork.

The fork is thus arranged to automatically control the energization of the magnet 52 so that the action of the fork will be continuous to supply a periodically variable current to the coil 53. Thecoil 53 is coupled to a a coil 56 in the nput, circuit of amplifier A62. The amplifier A-62 may be, for example, aspacedischarge amplifier operating on the straight portion of its input voltageoutput current characteristic. The harmonic producer HG-63 may be of any suitable type, as for example, the non-oscillatory electric space discharge harmonic generator disclosed in Vennes Patent. 1.485.650, March 4, 1924. In the output circut of the harmonic producer is a circuit 65 tuned to a frequency, say. 10,000 cycles per second. which is a harmonic of the frequency of oscillator O-51.

A Hartley oscillator O70 comprising an electric space discharge tube 70 has in its oscillation circuit a condenser 71 in parallel with inductance coils 72 and 73 in series.

The tuned circuit 65 is coupled to coil 73.

' and the oscillation circuit of tube 70 is tuned 35 approximately to the same frequency as circuit 65. Therefore. the osc llator is heldv in step with the 10,000 cvcle current in circuit 65. although the oscillator output is much greater than the power of the controlling harmonic.

Space current for tube 70 is supplied. by source through a choke coil 75, that has high impedance for the frequencies generated by 0-70. Condenser 7 6 is a stopping condenser which prevents battery 25 from being short circuited through coil 72. Condenser 77 in combination with resistance 79 produces proper biasing potent al for the grid of tube 70. A leak resistance 79 connects the grid and the filament of tube 70.

A harmonic generator I-IG85 comprising an electric space discharge tube 85 has its grid and filament connected across resistance 7 9 by a series condenser 86 and a shunt resistance 87. A source 88 supplies a large negative potential to the grid of tube 85 to cause the tube to generate pronounced harmonies. Space current for tube 85 is supplied by source 25 through the output coil 90 of the tube. A condenser 30 by-passes alternating current around the source 25'. The harmonic producer does not generate selfsustainedoscillations.

A Hartley oscillator O9l comprising an electric space discharge tube 91 has in its os cillation circuit a condenser 92 in parallel with inductance coils 93 and94 in series.

The coil 90 is coupled to coil 94, and the oscillationcircuit of tube 91 is tuned approximately to a harmonic of the frequency of oscillator 0-70 which is generated by harmonic'producer HG-85. Therefore, the oscillator is held in step with that harmonic, although the oscillator output is much greater than the power of the controlling harmonic.

Space current for the tube 91 is supplied by source 25 through a choke coil 39 that has high impedance for the frequencies generated by O91. The steady grid potential for this tube is determined by resistance 97.

A load circuit 95 of any suitable type is coupled to the coil 93 by a coil 96.

The power required to pull an oscillator into step depends upon the part of the circuit into which it is introduced and upon how much difference there is between the pulling frequency and the frequency at which the oscillator tends to work. A system works well in which the current for pulling an oscillator into ste .is introduced into the oscillation circuit 0 the controlled oscillator directly, as for example, at coils 90 and 94in Fig. 3; .but the pulling power is more effective if the control current is introduced in the grid circuits of the controlled oscillators, as for example, in Figs. 1 and 2. On some occasions it is possible to pull an oscillator into step even when the frequency at which the oscillator tends to operate differs from the frequency of the control current by as much as 10% and the pulling power is very much smaller than the power in the controlled oscillator. In arrangements as indicated in any of the figures of the drawings, the different oscillators or stages do not have to be of the same power capacity but, as is indicated above, may actually increase in power from the first towards the last and still secure frequency control.

What is claimed is:

1. In combination, an electric space discharge device, means for causing said device to generate self-sustained oscillations of fixed frequency, and an oscillation generator cou- 1-15 pled to said device, included in said last mentioned means, the power capacity of said device being large relative to that of said oscillation generator.

2. In combination, an oscillator of relatively low power capacity operating at a relatively low frequency, a second oscillator of relatively high power capacity, tuned ap proximately to a harmonic of said first frequency, means included in said first oscillator itself for producing said harmonic, and means coupling said oscillators for impressing said harmonic from said first oscillator on said second oscillator, whereby said first oscillator stabilizes the frequency of said second oscillator without the interposition of non-oscillatory high frequency amplifiers.

3. In combination, an electric s ace discharge device, means for causing said device to generate self-sustained oscillations of fixed f uency, and an oscillation generator coupie to said device, included in said last mentioned means, the power capacity of said device being large relative to that of said oscillation generator, eluding mechanically vibratile means stabilizing its frequency.

4. A si aling system comprising a relatively hig power oscillator, an oscillator for delivering relatively low power at a frequency having less variation than the frequency variation that said first oscillator would undergo in the absence of said second oscillator, and means coupling said oscillators for stabilizing the frequency of said first oscillator, the frequency to which one of said oscillators is tuned having an integral multiple of a frequency at which the other is tuned.

5. In combination, a generator of a wave of a fundamental frequency, a generator of a frequency equal to a harmonic of the fundamental frequency, means responsive to the single wave constituted by said wave of fundamental frequency for converting the fundamental frequency wave into a wave of a frequency which is a harmonic of the fundamental frequency equal to the harmonic generated by said second generator, and means for so inter-relating said converting for and said generator intively stable frequency,

connected to said generator to maintain substantially constantthe frequency thereof, a generator of waves of an approximately harmonic frequency, and means coupling said generators whereby the harmonic frequency is maintained constant.

9. In combination, an electric space discharge device means for causing said device to generate self-sustained oscillations of relaan oscillation generator of less stability and ofan approximately harmonic frequency, means responsive to said first oscillations to produce a harmonic thereof of approximately the fre uency of said oscillation generator, means for impressing said harmonic oscillations on said generator whereby the frequency stability of the latter is improved;

10. In a radio transmitting system, a plurality of amplifiers in tandem, each amplifier including a space discharge tube arranged to generate oscillations, resonant means individual to each tube for controlling the frequency of oscillations in each tube, and means cooperating with all said resonant means for maintaining the frequency of oscillations substantially constant.

In witness whereof, I hereunto subscribe my name this 16th day of August A. D., 1927.

GEORGE M. THURSTON.

means and said second generator that the frequency of said second generator is maintained in synchronism with the harmonic produced by said converting means.

6. A signaling system comprising a relatively high power oscillator, an oscillator for delivering relatively low power at a frequency having less variation than the frequency variation thatsaid first oscillator would undergo in the absence of said second oscillator, and a non-oscillatory harmonic generator coupling said oscillators for stabilizing the frequency of said first oscillator, the frequency to which one of said oscillators is tuned being an integral multiple of a frequency to which the other is tuned.

7. In combination, an oscillation generator operating at a relatively low frequency, a second oscillation generator tuned approximately to a second frequency which is a harmonic of said first frequency, an oscillator adjusted to oscillate approximately at a third frequency which is a harmonic of said second frequency, means for causing said first oscillation generator to control'the frequency of said second'oscillat-ion generator, and means for causing said second oscillation generator to control the frequency of said oscillator.

8. In combination, a generator of continuous oscillations, mechanically vibratile means

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